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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

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In order to judge of the potability of a water, a partial or complete
analysis is made according to circumstances.

The former includes qualitative tests for ammonia, nitrates and phos-
phates, and determinations of the fixed residue, hardness and organic
matter. Complete analysis requires, in addition, determinations of the
dissolved gases and of the various mineral components (chlorine, sulphuric
acid, silica, lime, magnesia, alkalies, etc.).

In either case great importance attaches to the taking of the sample
and the observation of the physical characters of the water.

Taking of the Sample.—The sample should be collected in a new
bottle of colourless glass with a ground stopper. This is washed first with
pure hydrochloric acid, then repeatedly with ordinary water (the bottle
being completely filled twice), and lastly with distilled water, and, when
the sample is taken, it is well rinsed with the water to be analysed. Corks
may be used, but these should be new and either well washed with the par-
ticular water or, better, waxed. Coloured glass bottles, especially after
use, are to be excluded absolutely, as also are earthenware or metallic

To take a sample from a spring, river, reservoir, or well, the vessel should,
where possible, be immersed in the water, care being taken not to collect
the surface layer or the deposit at the bottom.

Where another vessel is used to transfer the water to the bottle, it must
be thoroughly cleaned and then rinsed with the water itself.

Before taking a sample from a tap or pump the water in the pump or
in the tube of the tap must be run away.

In the case of a spring, the surroundings must be examined—the nature
of the soil and especially any cultivated ground, habitations, cemeteries,
or other possible source of contamination which may be near.

With rivers the distance from the source and the course (whether through
inhabited or industrial districts, etc.) are noted, together with the geological
character of the ground.

In the case of wells or reservoirs, observations are made on their depth,
the kind of wall, the nature of the sub-soil, and the distance from sewers
or other source of contamination.

For partial analysis, 3-4 litres of water are sufficient, whilst complete
analysis requires about 20 litres.

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